1. Field of the Invention
The present invention relates to a touch sensor for measuring the position of an object to be detected, such as a cutting tool used in an NC lathe or the like.
2. Related Art Statement
As is well known, for instance, an NC lathe, a manufacturing line, or the like is generally provided with a plurality of touch sensors respectively having projections in a plurality of directions in correspondence with the directions of movement of objects to be detected such as cutting tools, members or the like in order to detect the positions of the objects to be detected.
A conventional technique concerning this touch sensor will be described with reference to FIGS. 9 and 10. Plungers 3a, 3b, 3c, 3d are provided at one end of a column 2 detachably secured to, for instance, a bed of a lathe via a fixing member 1 in such a manner as to be disposed perpendicularly of the column 2 and project in four directions. Contacts 4a, 4b, 4c, 4d formed of a carbide tool material are respectively fitted to the centers of the tips of the plungers 3a-3d. In addition, the end surfaces of the contacts 4a to 4d which are more remote from the shaft 2 are formed to a high level of precision.
This touch sensor is disposed in the vicinity of, for instance, a chuck of a lathe. If an object to be detected such as a cutting tool, is brought into contact with any of the contacts 4a to 4d, a trigger signal is to be output from the touch sensor.
With this conventional technique, however, since the contacts 4a to 4d are respectively fitted to the tip portions of the plungers 3a to 3d, the distance between the respective opposing ones of the contacts 3a to 3d, i.e., the dimension A shown in FIGS. 9 and 10, becomes large.
For this reason, when the position of a cutting tool or a member is detected, it is necessary to enlarge the distance between the object to be detected and the contacts. If the distance between, for instance, the cutting tools to be detected is small, there is the possibility that it becomes impossible to effect detection due to the large dimension A, and the setup of an operation is disadvantageously restricted as a result.
In addition, since it is necessary to cause the plungers to project from the column and to install the contacts to the respective tips thereof, production costs are liable to increase.